[masraum]

Originally Posted by stomachmonkey

Desiccant.

Wrap it tight in plastic with a full bag of rice for a couple of days.

I vote replace.

If you're going to go that route, buy some actual dessicant, much, much more effective than rice.

I agree, if it's an option, replacing sounds like the best option. Other than a bad master cylinder that's allowing brake fluid to leak into the thing which is the most common cause, but usually includes a big loss of brake fluid, where's the water coming from? Why/how is the booster filling up so much?

If the replacement deal is about cost, how about a used part from a junk yard, but then you don't know if that's good or not.